With increasing development of bioengineering technologies, many valuable funguses, plants or their secondary metabolites are propagated and produced in bioreactors. Most of bioreactors were used for propagating fungus hypha or plant cell. These bioreactors comprise stirred tanks, bubble columns, air-lift reactors, hollow-fiber membranes, liquid-dispersed trickle and incline reactors. Some of bioreactors were capable used to culture plantlet, for example mist bioreactors. As known, each of these bioreactors has several limitations. Take a conventional mist bioreactor for example. Referring to FIG. 1, the mist bioreactor 1 comprises a growth chamber 10, an ultrasonic mist generator 11 and a nutrient reservoir 12. In the growth chamber 10, a culture medium 13 has thereon explants 14 to be propagated, for example three plantlets. The nutrient solution of the nutrient reservoir 12 flows into the ultrasonic mist generator 11 and is energized by the ultrasonic mist generator 11, thereby creating nutrient mists. The nutrient mists are then discharged from a mist-exit port 101 and distributed over the plantlets 14. The locations of the mist-exit port 101 and the culture medium 13 are unchanged. As known, the mist-exit port 101 spreads more nutrient mists onto the middle shoot, while the bilateral shoots get less nutrient mists. Therefore, the plantlet 14 has different growth rate. In addition, the industrial application of such a bioreactor has been limited by a number of drawbacks including low product yields and difficulty in scale-up.